This invention relates to the art of coupling devices between a gas supply tank and gas consuming equipment and, more particularly, to a coupling for connecting the cylinder valve of an LPG tank to a pressure regulator for delivering gas to gas consuming equipment.
The use of LPG tanks as a gas supply for outdoor grills, gas consuming equipment in motor homes and the like is well known as is the fact that the flow of gas from the tank to the gas consuming appliance is through a cylinder valve mounted on the tank, a pressure regulator connected to the appliance and a quick connect coupling between the outlet side of the cylinder valve and the inlet side of the pressure regulator. The latter coupling comprises a nipple component having a gas flow passageway therethrough, an inlet end for connecting the nipple to the cylinder valve through the use of a coupling nut, and an externally threaded outlet end for connection to the pressure regulator. When the coupling is connected to the cylinder valve, the upstream end of the nipple engages and displaces a check valve in the cylinder valve from the closed to the open position thereof permitting flow of gas from the tank through the coupling to the pressure regulator and gas consuming equipment. The coupling, when connected between the cylinder, valve and pressure regulator, is required by UL and other agencies to have a gas flow limiting valve arrangement for shutting off flow from the LPG tank in response to a pressure differential of no more than 15 psig across the valve. The coupling is also required to have a temperature activated arrangement for positively shutting off the flow of gas from the LPG tank in response to exposure of a coupling to a temperature between 240xc2x0 F. to 300xc2x0 F. at a gas pressure in the tank of 375 psig. Accordingly, if for example a fitting breaks downstream of the cylinder valve, the pressure drop across the flow control valve will immediately shut off the flow from the LPG tank. Likewise, should the coupling be exposed to an unacceptably high temperature, the nipple will be displaced from the cylinder valve, without unscrewing the coupling nut, a distance at least sufficient to allow closure of the check valve in the cylinder valve.
Efforts heretofore to meet the excess flow shutoff requirement have included the use of a magnetic valve element mounted in the nipple as shown in U.S. Pat. No. 5,330,155 to Lechner. The valve element is a ferrous plate normally held upstream from a valve seat by a magnet mounted in the nipple passageway. In response to excess flow across the valve, the plate is displaced from the magnet to engage against the valve seat and shut off the flow of gas through the nipple. When the gas pressure is equalized on opposite sides of the plate, the latter is drawn back into engagement with the magnet to again open the nipple passage for the flow of gas therethrough. The disadvantages and potential problems in connection with the Lechner arrangement include the cost of manufacture and the potential for the valve to malfunction in response to excess flow thereacross. In part in this respect, the magnet component for holding the magnetic disk has to be mounted in the passageway through the nipple and appropriately positioned relative to the valve seat, and when the valve element is displaced from the magnet by excess gas flow there is the potential that the magnetic disk will turn in the passageway and therefore fail to engage the valve seat transverse to the axis of the passageway as is necessary to shut off flow through the nipple.
Efforts heretofore to meet the foregoing requirement for the shutoff of gas flow in response to exposure of the coupling nut to an excessive temperature have included the provision of the end wall of the coupling nut with an axially extending circumferential recess or other weakening arrangement of the wall. In response to the exposure of the coupling nut to an excessively high temperature, the end wall is axially distorted by the pressure of the gas flow from the tank and the force of the check valve biasing spring against the nipple, whereby the latter is released or displaced outwardly relative to the coupling nut a distance sufficient to disengage the check valve and thus shut off the flow of gas from the tank to the coupling assembly. Arrangements of this character are shown in the aforementioned patent to Lechner and in U.S. Pat. Nos. 4,911,194 to Lechner and 5,582,201 to Lee, et al. The disadvantages with regard to weakening the end wall of the coupling nut by axially recessing or thinning the axial dimension of the end wall, whether the coupling nut is made of plastic or metal is that the end wall can be pre-stressed or broken during screwing of the coupling nut onto the cylinder valve. If the weakened end wall is broken during assembly, the assembly cannot be completed without replacement of the coupling nut. If the weakened end wall is pre-stressed during assembly, then there is the potential for the release of the nipple to occur at a temperature below that intended and, therefore, at a temperature which is below that required in accordance with the safety standards.
The present invention provides a coupling for connecting the cylinder valve on an LPG tank with a pressure regulator for supplying gas to gas consuming equipment having improved excess flow and thermally responsive shutoff arrangements which minimize or overcome the foregoing and other disadvantages of such shutoff arrangements heretofore available. More particularly in this respect, an excess flow shutoff valve in accordance with the present invention comprises a planar valve plate, preferably of stainless steel, axially captured between components of an insert for the nipple component and operates like a leaf spring. The valve plate is spaced upstream from a valve seat provided on one of the insert components and, normally, is in a planar condition transverse to the axis of the passageway through the nipple. In response to excessive gas flow through the nipple, the valve plate is distorted downstream against the resiliency thereof to a concave condition engaging the valve seat and shutting off the flow of gas through the nipple. The excess flow responsive valve is economical to manufacture and assemble both with respect to the component parts thereof and the assembly of the insert with the nipple, and the valve is reliable and efficient in operation. Further in accordance with the present invention, the thermally responsive shutoff arrangement advantageously involves the use of the end wall of the coupling nut but without weakening of the latter such that the shutoff function does not take place in response to a condition, including temperature, other than that sought in connection with meeting the required safety standards. More particularly in this respect, the axially inner side of the end wall is associated with a heat transfer component, preferably in the form of a metal washer. The end wall and heat transfer component engage against a shoulder on the nipple and thus against the gas pressure and check valve biasing spring force when assembled with the cylinder valve, and the heat transfer component advantageously rigidifies the end wall against undesired pre-stressing thereof when the coupling nut is screwed onto the cylinder valve and/or premature axially outward distortion of the end wall in response to a temperature below that desired for release. Furthermore, the heat transfer element advantageously promotes the transfer of heat to the end wall and thus the desired axially outward distortion thereof in response to a predetermined temperature and, in doing so, enables the axial thickness of the end wall to be optimized in connection with obtaining structural integrity thereof against undesired axial distortion and/or pre-stressing in connection with attaching the nipple to the cylinder valve.
It is accordingly an outstanding object of the present invention to provide a coupling for connection between the cylinder valve of an LPG tank and a pressure regulator for delivering gas to gas consuming equipment having improved excess flow and thermal responsive gas flow shutoff arrangements.
Another object is the provision of a coupling of the foregoing character in which the excess flow shutoff valve operates in the manner of a leaf spring which is transverse to the direction of gas flow and thus reliable in operation.
Still another object is the provision of a coupling of the foregoing character wherein axial displacement of the end wall of a coupling nut in response to exposure thereof to a predetermined high temperature is promoted by a heat transfer element facially engaging against the inside surface of the end wall.
A further object is the provision of a coupling of the foregoing character in which the thermally responsive shutoff arrangement includes the use of a heat transfer component in connection with the end wall of the coupling nut in a manner which rigidifies the end wall against pre-stressing or undesired axial distortion when the nipple is connected to the cylinder valve while providing for the end wall to be axially displaced to release the nipple from the check valve of the cylinder valve in response to exposure of the coupling nut to a predetermined temperature.
Another object is the provision of a coupling of the foregoing character in which the excess flow and thermally responsive gas shutoff arrangements are simple in construction, economical to manufacture and reliable in use.